class F1(object):
    def show(self):
        print ('F1.show')


class S1(F1):

    def show(self):
        print ('S1.show')


class S2(F1):

    def show(self):
        print ('S2.show')


def Func(obj):
    print (obj.show())


s1_obj = S1()
Func(s1_obj)

s2_obj = S2()
Func(s2_obj)
